Which Chair Config is More Stable: Axial or Equatorial?

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In summary, the question was about the stability of two conformational isomers (A and B). The first chair of B was considered more stable because it had 1 equatorial position while A had none. However, for the second chair, A was more stable with 3 equatorial positions compared to B's 2. After considering all four chairs, it was determined that A was the most stable conformer.
  • #1
Sslsn
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The question asks which is the more stable conformational isomer (A or B). i drew both chair configurations for each (see pic below). For the first chair, isn't B more stable because it has 1 eq. while A has none? For the second chair, isn't A more stable because it has 3 eq, and B only has 2?

How do you determine overall which is more stable after drawing all 4 chairs (correct answer is A)?http://i.imgur.com/V5zHt.png
 
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  • #2
Yes, the confomer of A that has 3 axial methyl groups has higher energy than the confomer of B that has only 1 axial methyl group.

That is not the question. Your question was what compound is more stable. You look at the most stable conformer of each compound and compare only those two structures.
 

Related to Which Chair Config is More Stable: Axial or Equatorial?

1. What is the difference between axial and equatorial chair configurations?

The axial and equatorial chair configurations refer to the orientation of substituents on a cyclohexane molecule. In the axial configuration, the substituents are pointing up or down, while in the equatorial configuration, they are pointing outward from the ring. This can also be thought of as the substituents being in the "axial" or "equatorial" positions relative to the ring.

2. Which chair configuration is more stable?

The equatorial chair configuration is generally more stable than the axial chair configuration. This is because in the equatorial position, the substituents experience less steric hindrance (repulsion between atoms or groups) from each other, leading to a lower energy state.

3. What factors affect the stability of chair configurations?

The stability of chair configurations is affected by the relative sizes of the substituents, the number of substituents, and the presence of any bulky groups. These factors can affect the amount of steric hindrance and strain on the molecule, which can impact its stability.

4. Can the stability of a chair configuration be predicted?

Yes, the stability of a chair configuration can be predicted using computational methods, such as molecular modeling. These methods can calculate the energy of each configuration and determine which one is more stable.

5. Are there any exceptions to the general rule that equatorial configurations are more stable?

Yes, there are some exceptions to this rule. In some cases, the presence of bulky substituents may actually make the axial configuration more stable. Additionally, in certain ring systems, such as bicyclic compounds, the stability of chair configurations may be influenced by other factors beyond steric hindrance.

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